Actually Matt is right, the US (and Canadian) standard is 120Volts AC +/- 5% (which is 114 to 126 Volts) at 60 Hertz.
Way back in the early days, Edison (who won the power battle with AC power over Tesla’s DC), had set the standard at 110 VAC to ensure that houses at the end of lines could at least get 100 VAC and many appliances were labeled that way but the standard was changed to 115V in about the 1930’s and then in 1984, the NEC mandated 120V +/- 5%. It has been creeping up to make power transmission more efficient with the existing gauges of wire used.
Normal residential power is delivered as single phase from each leg of the transformer at 120 VAC to neutral with the other leg to neutral being 180 degrees out of phase (so the two hot wires together will give 240 VAC - still at 60 Hertz). Industrial systems (and some marinas) use 3 phase power because it is more efficient and that system has three hot legs, each of which is at 120 VAC to neutral but 208 VAC to another leg as the power is out of phase by only 120˚. Think of the power as coming in on a Sine wave oscillating at 60 Hertz. When you combine those three phases together you get 360 degrees (or 120 degrees on each of three legs). The net of it is that your boat can see anything from 208 to 240 VAC if you join two hot legs together or 120 VAC if you just use one hot leg to neutral. All 60 Hertz and +/-5%.
Most devices labelled 110VAC will have no difficulty at all at 120VAC. NEMA rated motors will go +/- 10% of their nameplate voltages. Old incandescent bulbs might burn a bit hotter (as might the element on your stove or hair dryer) but the motors will take to it just fine as will your electronics.
Brent Cameron, Future Amel owner & Amel Owner's Registry Moderator
Future Amel Owner & Amel Owner Registry Moderator
Oro-Medonte, Ontario, Canada